The Optimization of a Volute Downstream of a Vaned Radial Compressor

Volutes downstream of radial compressor impellers and their respective diffusors have proven to be useful flow geometries, as they collect and deflect the swirling mass flow efficiently and feature a compact shape. Whilst a good preliminary design of a volute can be found by means of the conservation of mass and angular momentum at the diffusor outlet, the pursuit of ever-increasing efficiencies raises the question of which design methods are best suited to find these designs. The combination of automatized optimization and reliable computational fluid dynamics appears promising. Hence, three different optimization strategies are tested, their pros and cons discussed and their results compared. Two of the methods exploit the adjoint method to determine gradients. They both prove to be superior in terms of computational effort and design improvement. Both algorithms suggest a prominent design change that concerns the volute tongue. It is moved away from the impeller in a way that it homogenizes the static pressure at the diffusor vane inlets and leads to an overall reduction in pressure drop.